The present invention relates generally to medical testing methods, and more specifically to the use of a brown recluse spider (Loxosceles reclusa) toxin treated human plasma as a positive control, or standardized reference, for lupus anticoagulant blood tests.
Lupus anticoagulants are antibodies that interfere with blood coagulation, or clotting. Curiously, they are anticoagulants only in vitro, or outside the human body. In vivo, or inside the body, they act to increase the risk of thrombosis, or detrimental blood coagulation inside the heart, arteries, veins or capillaries. Lupus anticoagulants are found in the blood of many persons, and not merely in the blood of persons suffering from systemic lupus erythematosus, an inflammatory autoimmune disorder from which lupus anticoagulants derive their name. While persons having lupus anticoagulants present in their blood often show no adverse symptoms, a significant percentage of such persons will suffer from such complications as thrombosis, seizure disorders and, in women, spontaneous abortions.
Unfortunately, testing blood for the presence of lupus anticoagulants is very inexact. Present tests or assays used for detecting lupus anticoagulants, which generally test in vitro for various impaired coagulation indicators, can give misleading results from, for example, the presence of mild blood factor deficiencies. Blood factors are contributors to beneficial blood clotting and a deficiency in any one of many such factors will reduce clotting both in vivo and in in vitro tests so that they can produce, in vitro, the same test results as lupus anticoagulants. Vice versa, a mild blood factor deficiency may be misdiagnosed as the presence of a mild lupus anticoagulant. To most accurately test blood plasma samples for lupus anticoagulants, a standardized positive control is required for calibration and comparison of both testing equipment and technique. Because blood plasma with a lupus anticoagulant is not easily stored, and because patients with a lupus anticoagulant for obtaining blood samples are not always convenient, there is a need for a commercially available control plasma that accurately mimics the effects of a lupus anticoagulant in human plasma for laboratory testing. Without such a positive control, laboratory technicians cannot be certain that their testing for the presence of lupus anticoagulants is indeed performed in a manner consistent with expected results.
Treatments for complications from the presence in blood of correctly diagnosed lupus anticoagulants are generally successful. It is important, therefore, that accurate tests for the presence of lupus anticoagulants be available so that patients will receive the appropriate, and not a harmful, treatment for their illness.
It is, therefore, a principal object of the present invention to provide a method for performing accurate blood tests for the presence of lupus anticoagulants by the use of a positive control plasma that mimics the effects of a lupus anticoagulant in human plasma.
It is another object of the present invention to provide a method for preparing the positive control plasma that makes it readily available for commercial use.
A feature of the present invention is that its use of brown recluse spider toxin treated blood plasma can be extended for use as an all purpose abnormal control for defects of all the coagulation factors of the intrinsic clotting system. Its use will greatly increase the accuracy and sensitivity of all such tests.
Another feature of the present invention is that a very small amount of spider venom and the toxin produced from it will treat a large amount of blood plasma.
An advantage of the present invention is that its positive control plasma is prepared from normal donor plasma, reducing the possibility of HIV and hepatitis, and overcomes the limited availability of lupus anticoagulant plasma donors.
Another advantage of the present invention is that separate batches of the plasma can be made over time with equal and controlled potency. Plasma taken from even a single lupus anticoagulant donor will vary in potency from donation to donation.
A further advantage of the present invention is that it is a single abnormal control or standard. Other methods may require multiple controls.